Doing more research on the lighting device I want to create, i need some assistance.
AS the XHP-70 is the current most efficient high power diode 150lumens/watts, i plan on using a few of them for the project i want to create.
The plan is 15000-20000lm output. The XHP-70 can produce 4000lm each.
What option would be the best efficiency in terms of lumens output and heat?
Option 1:
Push Led diode to max 4000lm (32w designed) and use only 5 units of xhp-70 to produce 20000lm
Option 2:
Push Led diode to 80-90% of its designed power so that heat is reduced and possibly longer lasting diode life and use 6 units of xhp-70.
Does the XHP-70 constantly have 150lm/w even with lower power delivery? So if i provide only half the power, will it still deliver efficiency at 150lm/w?
The efficiency of LED emitters isn’t static. It is affected by how much wattage you give it, but also heat. Look at the Cree PCT for better understanding of the lm/w efficiency range of emitters. Also, as mdeni showed, Cree LEDs can be run well above their official rating for more light output than you’ve ever dreamed. But, to do so, you need to make sure they’re mounted on Direct Thermal Path MCPCB’s to get the heat away from the emitter and out to the host where it can be dissipated effectively.
Well, we do actually have Custom MCPCB manufacturers as members here now. You can look it up using the search box at the upper left of the screen. But, you don’t need to put them all on one MCPCB. There’s nothing wrong with using individual MCPCB’s for this.
Yeah, it will definitely be a lot of heat. If you want the best possible performance, use Copper DTP MCPCB’s and a thick copper shelf under them. Aluminum shelf would work fine, too, but copper has about double the thermal conductivity.
Lumens per watt decreases as output increases, as evident in the downward curve of the graph. This is true of all LEDs. MAX ratings are typically given at a fairly low output as well, around 10-15% of maximum. Also Djozz tests show ballpark output mounted on a large heat sink so unless you can duplicate that and keep it cool over time you won’t get the same results. In other words, more LEDs at lower current is better for output.
Bruno28, as Rufusbduck has said one does not simply gets 5000 lumens out of some random XHP70 without at least using a hulksink plus a top-notch baseplate…
You'd just need a relatively moderate driving current for such arrays to perform nicely. Let's conservatively assume the emitters are R2 bin, that means 118 average lumens per emitter at 350mA; at 1A we get 2'4x that amount: 283'2lm/emitter × 42 emitters = 11894'4 lumens each array. Vf on each array would be close to 45V, at 3A of current.
There are some affordable desktop computer heatsink/fan combos who would (more or less) cope with such a load, especially if we reduce the emitter driving current to ≈833mA/emitter (2'5A/array), which would still get us, in theory, ≈10856 around 9912 lumens/array. Higher efficiency, and less than 110W per module.
Hope this helps.
Cheers ^:)
Original posting date: Wed, 08/31/2016 - 23:52; edited to fix a calculation error.
Would i be able to get away with no fan cooling? But i would use a nice big heat sink, probably aluminium or copper. The device I want to create will be used for night work lighting. So it need to be water resistant, and adding a fan will not allow water resistant.
Edited my previous post Bruno28, fixed the lumen output estimate for the 42 piece module driven at 2'5A (9912 lumens).
Well, I think your best bet then would be purchasing a whopping 4 modules. Driving them at baseline (binning) driving current, each one would deliver ±118×42≈4956lm, while dissipating (39'9V × 1'05A) 41'895W, something which could be reasonably well managed with a decent passive heatsink.
Enclosures? Lenses? Power sources?
Honestly, you can get AC powered ready made led lamps which are quite cost effective. Just buy a bunch of 'em:
What about those 100w cob led? They semester to produce 9000 to 10000 lumens. Two of those would be nice and floody. Simpler to design something. But not as efficient. Are they any good?
You mean those sheesh-CRI cheapass led arrays? I'm not touching on that stuff, standard sheeshy (Cree) led CRI is already enough for me.
Get some high quality (high CRI) emitters instead. Just saw the video and took a peek at the Yuji store, cool (and expensive) stuff.
0K, this may have sounded a bit off-topic but, know what? It remembered me FastTech is stocking pretty fairly priced eggsNichia 219A emitters, and I bet you my kingdom you may be able to get well under $2 price for a 3-pack if requesting a wholesale 40+pack inquiry. These leds may give you ≈180lm at 1A so, 120 leds × 180lm/led ≈ 21600lm of pleasing 92+CRI light. Of course, assembly of such a thing would require some bigass can of elbow grease…
By the way, pics of my less than $25 kitchen lamp custom retrofit:
Cool whites at the center held by ∅8×1'5mm neodymium magnets, and driven at half nominal current because of thermal reasons with a 18-36W driver (30W here). At the sides: 2×10W warm white Markerled lamps from banggood. Pleasing white combined colour temperature and better than standard Cree CRI I'd say without a doubt…
Is there a size constrain? Spreading out the emitters on the mounting plate will ease cooling concerns. All pointed one direction or ring mounted. Another way to go would be led tape spiral mounted on an aluminum tube like a barber pole.
Well this is my current prototype design I made yesterday. It would be 6 units of XHP-70 with a TIR lens that should be able to drop in the wholes and give a nice wide beam. Should be closer to 24000lm in a compact size if run at 2.4 amps. The whole body is aluminium so it will be an added bonus for heat dissipation, but there will be a 150 by 100 heatsink at the back.
Yes some active cooling seems in order here
You could go fancy and use PC water cooling parts to become a relative small part for the LEDs with a big heavy part for the radiator fans and cells.
Mount the led part on a pole that can be set to different angles to make a nice work light.
Use a metal covered shower hose (3 pieces) to guide the wires and water in and water out tube so these parts are not only protected but also looks neat.
